The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
During processing of substrates such as semiconductor wafers, ion implantation may be used to create a junction. During ion implantation, ions of a desired dopant species are accelerated into the substrate. For example, a substrate including an exposed layer of germanium (Ge) may be doped with phosphorous (P) species using an ion implantation process or I2P. Antimony (Sb) species can also be co-doped with phosphorous (P) species using I2P to increase P levels in Ge. However, it is difficult to form an ultra-shallow junction (USJ) that is less than 10 nanometers (nm) in depth using I2P due to high energy used during an implantation process. Furthermore, the doping steps are typically followed by annealing at high temperatures, which causes further diffusion into the Ge. In other words, the implanted ions diffuse beyond the desired USJ depth.